1. Field of the Invention.
The present invention relates generally to improvements in apparatus and methods for recognizing characters printed in magnetic ink on documents, an more particularly but not by way of limitation, to improvements in write heads for apparatus of the designated type.
2. Brief Description of the Prior Art.
The automated recognition of characters printed in magnetic ink on documents of various types and for various purposes has been well developed in the years since the adoption of the digital computer as a standard business tool. For example, it is now common practice among banking institutions to provide customers with checks that have been imprinted with a customer identification number in magnetic ink so that the checks can be rapidly sorted by machine. Checks received by the bank are passed through a character recognition system which provides electrical signals to a computer which operates sorting apparatus. An example of a character recognition system has been disclosed in U.S. Pat. No. 3,638,238 issued Jan. 25, 1972 to Milford et al, the teachings of which are hereby incorporated by reference.
In general such systems are comprised of a write head that includes a permanent magnet and pole pieces curving toward each other from the poles of the magnet to form a gap about which a magnetic field exists so that characters on document can be magnetized by passing the document across the gap. The document is then passed across a read head which senses changes in magnetic flux caused by motion of the magnetized characters by the read head and generates electrical signals that can be decoded by appropriate circuitry for transmission to a computer.
As indicated in the referenced U.S. Pat. No. 3,638,238 printing imperfections can result in problems in the recognition of a number printed on a document, and such imperfections have, in the past, required the use of high quality printers for imprinting the characters on documents. In general, printers employing xerography have not been suitable for printing magnetic characters on documents, and attempts to use such printers have led to excessive reject rates for documents being sorted. While the quality of xerographic printing has improved with the advent of so-called laser printers, it has still not been possible to rely on xerographic printers as a means of printing magnetic characters on documents prior to sorting or other operation involving the recognition of the characters. Accordingly, it has not been possible to reduce the cost of preparing documents for such recognition to a level based on the advances that have occurred in xerographic printing techniques.